Approximation of a sum

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I would like to approximate (or calculate) the below sum.

$$ \frac {1} {{2 N \choose M}} \, \sum_{k = 1}^{N / 2} \frac {2^{2 k}} {2 k} \, {N \choose 2 k} \, {N - 2 k \choose \frac {M - 2 k} {2}} $$

Do you know any methods I could use? Thanks